Vol. 62.] EOCKS OF WESTERN CAEEMAETHENSHTEE. 621 



there is evidence of their being inverted. This was probably brought 

 about by an overfold from the north developed into a thrust. Here 

 begin the complicated overfolding and faulting that have so much 

 disturbed the country farther west. This outcrop is cut off by a 

 low-hading fault — the thrust, in the dingle south of Penlan ; but it 

 comes to the surface again about a furlong farther west, abundant 

 striped fossiliferous debris in the soil indicating its whereabouts. 



The beds are exposed on the main road north-west of Penlan, 

 and a quarry has been opened in them on the side of the hill south 

 of Caerlleon. Higher beds are exposed on the top of the hill, but 

 on the northern slope a thrust has brought up the Didymograptus- 

 Murchisoni Beds and has carried them forward so as to overlap 

 some of the higher beds. Both outcrops are cut off on the slope 

 overlooking Melin Nant-yr-eglwys, Didymograptus-bifidus Beds 

 being exposed at several points on the slope below. 



At Nant-yr-eglwys there are at least four distinct outcrops. One 

 passes through the yard, and is flanked on both sides by higher 

 beds — a fact which suggests a small anticlinal fold, but a much 

 broken one. The other outcrops are formed of dismembered 

 portions of the main outcrop, cut up by buckling and faulting. 



Down in the valley, south-east of Nant-yr-eglwys, is a small 

 opening in the upper division of the beds, with some ash-debris 

 below. Prom here the outcrop sweeps in a curve along the brow 

 of the hill above Llethr-madyn and Fronboeth, to a point about a 

 furlong north of Clynpebyll, where it is cut off by a fault. There 

 is a short break in the outcrop due south of Nant-yr-eglwys, 

 where the beds are shifted northwards for a distance of about 

 200 yards, and are seen in the lane. 



From the point where the D.-Murcliisoni Beds disappear near 

 Clynpebyll to another point near Hafod Llanboidy, higher beds, 

 including Dicranograptus-Shales and Asaphus-tyr •annus Ash, are 

 faulted against Didymograptus-bifidus Mudstones ; but at the latter 

 place D.-Murchisoni Beds come to the surface once more, and are 

 traceable as far as a point a short distance south of Maesgwyn-isaf, 

 where they enter a fault — not to appear again between this spot 

 and the Tave. 



On the north, another outcrop comes out of a fault at Pengaer- 

 fach, a quarter of a mile west of Llanboidy, where the D.-Mur- 

 chisoni Beds form a peculiar and prominent feature in a field near 

 the quarries in the ash. This outcrop strikes west, passing under 

 Maesgwynne House and appearing in the southernmost of the 

 Pensarn Quarries. The beds are again seen crossing the road to 

 the west, and in tne Fro wen Wood, where there is a complete 

 section across them. They are also seen in the dingle, and are 

 traceable up the hill on the west. They sweep northward with the 

 contour of the hill on the western slope, producing an unmistakable 

 and continuous line of debris. But west of Frowen they are cut 

 off by an east-and-west fault, which displaces the outcrop for about 

 400 yards, and renders the structure somewhat obscure. 



